How Did SEM Morph Into Paid Search?

About two or three years ago, I noticed more and more people saying SEM when they meant, to me, paid search. I’d hear people say things like “We do SEO and SEM,” as if SEO wasn’t a part of SEM. I found that grating. I’d usually chalk it up to people either making an innocent mistake or perhaps still being new to the space.
Recently, it’s only gotten worse. I also hear it from people from large companies that I’d say should know better. But this is where I have that “Am I swimming against the tide?” feeling. Maybe it’s me that just hasn’t adjusted. I’ll come back to that, but first, how did this change come about?
ajmalseotipsandtricks.blogspot.com